Northern Hawk Owl - Surnia ulula
Potential Species of Concern
Global Rank:
G5
State Rank:
S4
Agency Status
USFWS:
USFS:
BLM:
FWP Conservation Tier:
3
PIF:
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Copyright by Borror Laboratory of Bioacoustics, Department of Evolution, Ecology, and Organismal Biology, Ohio State University, Columbus, OH, all rights reserved.
General Description
Appropriately named, the Northern Hawk Owl more closely resembles an Accipiter hawk species than an owl, both in morphology and behavior. Dropping from a visible perch on a prominent tree, gliding low over the ground or in high-speed flight, its short-pointed wings and long tail give the appearance of a falcon-like bird (Duncan and Duncan 1998). Following the general reverse sexual size dimorphism found in most owls, the female of this species is larger than the male. Females are generally 37.2 to 44.7 cm in length, while males are approximately 36.0 to 42.4 cm (Duncan and Duncan 1998). Sometimes surpassing males in mass by as much as 17%, females generally weigh 340 grams, while males average approximately 300 grams (Earhart and Johnson 1970, McGillivray 1987). Beneath a fairly flat-topped head and deep v-shaped black and white speckled forehead, the grayish-white facial disc is framed in black. The iris is yellow, the bill is pale yellow to greenish-yellow, and the flesh of the heavily feathered feet is colored a deep slate-gray to black (Duncan and Duncan 1998). The back, wings, and head are brownish-black, spotted and streaked with white, while the white breast and belly are heavily and distinctly barred with brown.
The vocalization of the Northern Hawk Owl is variable and persistent during the breeding season. The display call of the male is a trilling, rolling whistling "ululululululul" lasting up to 14 seconds, while the female's advertising call is shorter and less constant in pitch and rhythm, with a hoarser and shriller quality (Duncan and Duncan 1998). This species is also known to express an alarm or screeching call, a trilling call, a yelping call, a lure call, a soliciting call, a hiss and chitter, and other vocalizations (Duncan and Duncan 1998).
Diagnostic Characteristics
Northern Hawk Owls are easily distinguishable from other species of owls by a long tail and fast, maneuverable flight. The posture of Northern Hawk Owls is more hawk-like than owl-like. Prominent perch selection and hunting by daylight are additional cues that differentiate this species from other owls. The unique shape of this bird, including its moderately wedge-shaped tail, and overall coloration and appearance make it unlikely to be confused with any hawk species (Sibley 2000).
General Distribution
Summary of Observations Submitted for Montana
Number of Observations: 67
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
Relative Density
Recency
Breeding
(direct evidence "B")
Breeding
(indirect evidence "b")
No evidence of Breeding
(transient "t")
Overwintering
(regular observations "W")
Overwintering
(at least one obs. "w")
(Records associated with a range of dates are excluded from time charts)
Migration
Movement into Montana is sporadic and migration into the state generally reflects irregular movements of individuals and may be in response to local changes in food availability. Observations in the state have occurred in late fall and winter (November-February), as well as late spring and early summer (May and June) (Lenard et al. 2003).
Habitat
Johnsgard (1986) indicates Northern Hawk Owls prefer post-fire habitat and open muskeg areas, with tall trees or snags for use as hunting perch sites. No other specific information is available on nest site selection in Montana.
Ecological Systems Associated with this Species
- Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (high, medium, or low) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2001, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system relative to the species’ range and habitat requirements;
- Examining the observation records for each species in the state-wide point database associated with each ecological system;
- Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of “observations versus availability of habitat”.
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were associated as using an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system,
even if point observations were associated with that system.
High, medium, and low habitat quality was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species in the literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignments of habitat quality.
If you have any questions or comments on species associations with ecological systems, please contact Bryce Maxell at
bmaxell@mt.gov or (406) 444-3655.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at:
http://mtnhp.org/requests/default.asp) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species’ known geographic range.
Literature Cited
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
- Foresman, K.R. 2001. The wild mammals of Montana. Special Publication No. 12. Lawrence, KS: The American Society of Mammalogists. 278 p.
- Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
- Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
- Maxell, B.A. 2000. Management of Montana’s amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
- Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
- Commonly Associated with these Ecological Systems
Forest and Woodland Systems
Grassland Systems
Open Water / Wetland and Riparian Systems
Shrubland, Steppe and Savanna Systems
Food Habits
Food habits have not been studied in Montana, but research from other studies have revealed that Northern Hawk Owls' diet often is dominated by voles (primary prey in Eurasia), but birds (up to grouse size) may constitute the major part of the diet in winter; juvenile Snowshoe Hares may be important during certain nesting stages (Rohner et al. 1995, Duncan and Duncan 1998). The main Microtus species preyed upon in North American include Alaska vole (M. miurus), Meadow Vole (M. pennsylvanicus), Tundra Vole (M. oeconomus), Long-tailed Vole (M. longicaudus), and Yellow-cheeked Vole (M. xanthognathus) (Duncan and Duncan 1998). Other small mammals and bird species that comprise the balance of their diet are numerous and may include shrews, moles, rabbits, hares, squirrels, mice, rats, lemmings, weasels, partridges, doves, woodpeckers, jays, robins, startlings, sparrows, buntings, blackbirds, grackles, and finches (Duncan and Duncan 1998).
Hunting, may occur during the day or night, and is similar to hawk species. The Northern Hawk Owl watches prey from a perch, strikes with a rapid dive, and returns to an elevated perch to consume the food item. The pellets of this owl species are relatively small (up to 7.5 cm long), gray, and coated in mucus (Nero 1995).
Ecology
Ecological studies have yet to be conducted in the state. However, information from other areas of the species' range shows Northern Hawk Owls tend to occur in the greatest numbers in areas with temporarily high prey populations and may move long distances in response to changes in prey abundance. Population density generally is low (e.g., 4 pairs in 200 square kilometers in Norway; 1 pair per 500 square kilometer in Sweden) (Johnsgard 1988) with a maximum of 3 nests per 100 square kilometers in southwestern Yukon, Canada (Rohner et al. 1995). Home ranges in Europe ranged from 140 to 848 hectares, average 372 hectares (Baekken et al. 1987). In southern Alberta, they establish winter hunting territories (Johngard 1986).
Reproductive Characteristics
Limited breeding records exist for Montana. The first record of breeding in the western U.S. occurred in Montana in May of 1990, when a brood of 4 recently fledged young were observed in Polebridge. The first nest was confirmed when one was found in West Glacier in 1994 (eight young, seven fledged), and a second nest was recorded in 1995 when a female was photographed at a cavity site (Wright 1996, Lenard et al. 2003). Reproductive studies of Northern Hawk Owls in other areas of their range have found nesting to be in unlined hollows or cavitys.
Northern Hawk Owls produces smooth, slightly glossy eggs that are white, infrequently with a hint of yellow, and are blunt elliptical-oval to elongate-oval in shape (Eckert 1974, Baicich and Harrison 1997). The average egg dimensions are 30.63 to 32.15 mm by 38.64 to 42.48 mm, and weigh an average of 21.6 grams (Mueller 1986). Egg-laying has been reported from late April to mid-June in Alaska and arctic Canada; early April to early June in Alberta (Johnsgard 1986, Duncan and Duncan 1998). Clutch size is up to 13 (mean brood size was 6.3 in Fennoscandia, 3.7 in Yukon, 5.5 in Alaska). Incubation, by the female, starts as soon as the first egg is laid and continues until the last hatches, in total, about 25 to 30 days. Both parents tend the young, which fledge in 25 to 35 days, but may not be fully independent until they are three months old. Survivorship of the later-hatched young is dependent upon food availability. In Europe, a second brood has been reported with the loss of the first clutch of eggs, but this behavior has not been reported in North America (Baicich and Harrison 1997, Duncan and Duncan 1998).
Management
No current management activities in Montana specific to Northern Hawk Owl are documented.
References
- Additional ReferencesLegend:
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American Ornithologists' Union. 1983. Check-list of North American birds, 6th ed. Amer. Ornithologists' Union, Washington, D.C.- American Ornithologists' Union. 1998. Check-list of North American birds. 7th edition. American Ornithologists' Union, Washington, D.C. 829 pp.
- Austen M.J. W., M.D. Cadman, and R.D. James. 1994. Ontario birds at risk: status and conservation needs. Federation of Ontario Naturalists and Long Point Bird Obs., Port Rowan, Ontario, Canada.
- Baekken, B. T., J. O. Nybo, and G. A. Sonerud. 1987. Home range size of Hawk Owls: dependence on calculation method, number of tracking days, and number of plotted perches. pp. 145-148 IN Nero, R.W., R. J. Clark, R. J. Knapton, and H. Hamre, eds. Biology and conservation of northern forest owls. USDA Forest Service General Technical Report RM-142, USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, Colorado.
- Baicich, P. J., and C. J. O. Harrison. 1997. A guide to the nests, eggs and nestlings of North American birds. Second edition. Academic Press, New York.
- Bent, A. C. 1938. Life histories of North American birds of prey. Part 2. U.S. Nat. Mus. Bull. 170. 482 pp., 92 pls.
- Clark, R. J., D. G. Smith and L. Kelso. 1987. Distributional status and literature of northern forest owls. Pp 47-55 in: Biology and conservation proceedings, Feb. 3-7, Winnepeg, Manitoba. Gen. Tech. Rep. RM-142, Fort Collins, CO. USDA, Forest Service.
- Duncan, J.R., and P.A.Duncan. 1998. Northern Hawk Owl (Sturnia ulula), In The Birds of North America, No. 356 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, Pennsylvania.
- Earhart, C. M. and N. K. Johnson. 1970. Size dimorphism and food habits of North American owls. Condor 72:251-264.
- Ehrlich, P., D. Dobkin, and D. Wheye. 1988. The Birder’s Handbook, A Field Guide to the Natural History of North American Birds. Simon and Schuster Inc. New York. 785 pp.
- Johnsgard, P. 1988. North American owls: biology and natural history. Smithsonian Inst. Press. 336 pp.
- Johnsgard, P. A. 1986. Birds of the Rocky Mountains with particular reference to national parks in the Northern Rocky Mountain region. Colorado Associated University Press, Boulder. xi + 504 pp.
- Lenard, S., J. Carlson, J. Ellis, C. Jones, and C. Tilly. 2003. P. D. Skaar's Montana Bird Distribution, 6th Edition. Montana Audubon: Helena, MT, 144 pp.
- McGillivray, W.B. 1987. Reversed sexual dimorphism in 10 species of northern owls. Pp. 59-66 In: Nero, Robert W.; Clark, Richard J.; Knapton, Richard J.; Hamre, R. H., eds. Biology and conservation of northern forest owls: symposium proceedings; 1987 February 3-7; Winnipeg, MB. Gen. Tech. Rep. RM-142. U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. Fort Collins, CO
- Mueller, H.C. 1986. The evolution of reversed sexual dimorphism in owls: an empirical analysis of possible selective factors. Wilson Bulletin 98:387-406.
- Nero, R.W. 1995. Notes on a wintering Northern Hawk Owl in Manitoba. Blue Jay 53:205-214.
- Rohner, C., J.N.M. Smith, J. Stroman, M. Joyce, F.I. Doyle, and R. Boonstra. 1995. Northern Hawk-owls in the nearctic boreal forest: prey selection and population consequences of multiple prey cycles. Condor 97:208-220.
- Sibley, D. A.. 2000. National Audubon Society The Sibley Guide to Birds. Alfred A. Knopf, Inc: New York, NY, 544 pp.
- Terres, J.K. 1980. The Audubon Society encyclopedia of North American birds. Alfred A. Knopf, New York. 1109 pp.
- U.S. Forest Service. 1991. Forest and rangeland birds of the United States: Natural history and habitat use. U.S. Department of Agriculture, Forest Service Agricultural Handbook 688. 625 pages.
- Wright, P.L. 1996. Status of rare birds in Montana, with comments on known hybrids. Northwestern Nat. 77(3):57-85.
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